1. Field of the Invention
The invention relates to bacterial antibiotic resistance. More particularly, the invention relates to compositions and methods for overcoming bacterial antibiotic resistance.
2. Brief Summary of the Related Art
Bacterial antibiotic resistance has become one of the most important threats to modern health care. Cohen, Science 257:1051–1055 (1992) discloses that infections caused by resistant bacteria frequently result in longer hospital stays, higher mortality and increased cost of treatment. Neu, Science 257:1064–1073 (1992) discloses that the need for new antibiotics will continue to escalate because bacteria have a remarkable ability to develop resistance to new agents rendering them quickly ineffective.
The present crisis has prompted various efforts to elucidate the mechanisms responsible for bacterial resistance. Coulton et al., Progress in Medicinal Chemistry 31:297–349 (1994) teaches that the widespread use of penicillins and cephalosporins has resulted in the emergence of β-lactamases, a family of bacterial enzymes that catalyze the hydrolysis of the β-lactam ring common to numerous presently used antibiotics. More recently, Dudley, Phariacotherapy 15: 9S-14S (1995) has disclosed that resistance mediated by β-lactamases is a critical aspect at the core of the development of bacterial antibiotic resistance.
Attempts to address this problem through the development of β-lactamase inhibitors have had limited success. Sutherland, Trends Pharmacol. Sci. 12: 227–232 (1991) discusses the development of the first clinically useful β-lactamase inhibitor, clavulanic acid, which is a metabolite of Streptomyces clavuligerus. Coulton et al (supra) disclose two semi-synthetic inhibitors, sulbactam and tazobactam, presently available. Coulton et al. (supra) also teaches that in combination with β-lactamase-susceptible antibiotics, β-lactamase inhibitors prevent antibiotic inactivation by β-lactamase enzymes, thereby producing a synergistic effect against β-lactamase producing bacteria.
Li et al., Bioorg. Med. Chem. 5 (9): 1783–1788 (1997), discloses that β-lactamase enzymes are inhibited by phosphonate monoesters. Li et al. teaches that better inhibitory activity is achieved by compounds with amido side-chains, but that such compounds suffer the disadvantage of hydrolytic instability. Li et al. discloses that benzylsulfonamidomethyl phosphonate monoesters exhibit better hydrolytic stability, but also significantly weaker potency against β-lactamase enzymes, than do the corresponding benzylamidomethyl phosphonate monoesters. Dryjanski and Pratt, Biochemistry 34:3569–3575 (1995) teaches that p-nitrophenyl [(dansylamido)methyl]phosphonate irreversibly inactivates the P99 β-lactamase enzyme, and describes its use as a mechanistic probe for studying the interaction of ligands with a second binding site of the enzyme.
The availability of only a few β-lactamase inhibitors, however, is insufficient to counter the constantly increasing diversity of β-lactamases, for which a variety of novel and distinct inhibitors has become a necessity. There is, therefore, a need for the ability to identify new β-lactamase inhibitors. The development of fully synthetic inhibitors would greatly facilitate meeting this need.